GNU Linux-libre 5.10.217-gnu1
[releases.git] / block / ioprio.c
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * fs/ioprio.c
4  *
5  * Copyright (C) 2004 Jens Axboe <axboe@kernel.dk>
6  *
7  * Helper functions for setting/querying io priorities of processes. The
8  * system calls closely mimmick getpriority/setpriority, see the man page for
9  * those. The prio argument is a composite of prio class and prio data, where
10  * the data argument has meaning within that class. The standard scheduling
11  * classes have 8 distinct prio levels, with 0 being the highest prio and 7
12  * being the lowest.
13  *
14  * IOW, setting BE scheduling class with prio 2 is done ala:
15  *
16  * unsigned int prio = (IOPRIO_CLASS_BE << IOPRIO_CLASS_SHIFT) | 2;
17  *
18  * ioprio_set(PRIO_PROCESS, pid, prio);
19  *
20  * See also Documentation/block/ioprio.rst
21  *
22  */
23 #include <linux/gfp.h>
24 #include <linux/kernel.h>
25 #include <linux/export.h>
26 #include <linux/ioprio.h>
27 #include <linux/cred.h>
28 #include <linux/blkdev.h>
29 #include <linux/capability.h>
30 #include <linux/sched/user.h>
31 #include <linux/sched/task.h>
32 #include <linux/syscalls.h>
33 #include <linux/security.h>
34 #include <linux/pid_namespace.h>
35
36 int set_task_ioprio(struct task_struct *task, int ioprio)
37 {
38         int err;
39         struct io_context *ioc;
40         const struct cred *cred = current_cred(), *tcred;
41
42         rcu_read_lock();
43         tcred = __task_cred(task);
44         if (!uid_eq(tcred->uid, cred->euid) &&
45             !uid_eq(tcred->uid, cred->uid) && !capable(CAP_SYS_NICE)) {
46                 rcu_read_unlock();
47                 return -EPERM;
48         }
49         rcu_read_unlock();
50
51         err = security_task_setioprio(task, ioprio);
52         if (err)
53                 return err;
54
55         ioc = get_task_io_context(task, GFP_ATOMIC, NUMA_NO_NODE);
56         if (ioc) {
57                 ioc->ioprio = ioprio;
58                 put_io_context(ioc);
59         }
60
61         return err;
62 }
63 EXPORT_SYMBOL_GPL(set_task_ioprio);
64
65 int ioprio_check_cap(int ioprio)
66 {
67         int class = IOPRIO_PRIO_CLASS(ioprio);
68         int data = IOPRIO_PRIO_DATA(ioprio);
69
70         switch (class) {
71                 case IOPRIO_CLASS_RT:
72                         /*
73                          * Originally this only checked for CAP_SYS_ADMIN,
74                          * which was implicitly allowed for pid 0 by security
75                          * modules such as SELinux. Make sure we check
76                          * CAP_SYS_ADMIN first to avoid a denial/avc for
77                          * possibly missing CAP_SYS_NICE permission.
78                          */
79                         if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_NICE))
80                                 return -EPERM;
81                         fallthrough;
82                         /* rt has prio field too */
83                 case IOPRIO_CLASS_BE:
84                         if (data >= IOPRIO_BE_NR || data < 0)
85                                 return -EINVAL;
86
87                         break;
88                 case IOPRIO_CLASS_IDLE:
89                         break;
90                 case IOPRIO_CLASS_NONE:
91                         if (data)
92                                 return -EINVAL;
93                         break;
94                 default:
95                         return -EINVAL;
96         }
97
98         return 0;
99 }
100
101 SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
102 {
103         struct task_struct *p, *g;
104         struct user_struct *user;
105         struct pid *pgrp;
106         kuid_t uid;
107         int ret;
108
109         ret = ioprio_check_cap(ioprio);
110         if (ret)
111                 return ret;
112
113         ret = -ESRCH;
114         rcu_read_lock();
115         switch (which) {
116                 case IOPRIO_WHO_PROCESS:
117                         if (!who)
118                                 p = current;
119                         else
120                                 p = find_task_by_vpid(who);
121                         if (p)
122                                 ret = set_task_ioprio(p, ioprio);
123                         break;
124                 case IOPRIO_WHO_PGRP:
125                         if (!who)
126                                 pgrp = task_pgrp(current);
127                         else
128                                 pgrp = find_vpid(who);
129                         do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
130                                 ret = set_task_ioprio(p, ioprio);
131                                 if (ret)
132                                         break;
133                         } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
134                         break;
135                 case IOPRIO_WHO_USER:
136                         uid = make_kuid(current_user_ns(), who);
137                         if (!uid_valid(uid))
138                                 break;
139                         if (!who)
140                                 user = current_user();
141                         else
142                                 user = find_user(uid);
143
144                         if (!user)
145                                 break;
146
147                         for_each_process_thread(g, p) {
148                                 if (!uid_eq(task_uid(p), uid) ||
149                                     !task_pid_vnr(p))
150                                         continue;
151                                 ret = set_task_ioprio(p, ioprio);
152                                 if (ret)
153                                         goto free_uid;
154                         }
155 free_uid:
156                         if (who)
157                                 free_uid(user);
158                         break;
159                 default:
160                         ret = -EINVAL;
161         }
162
163         rcu_read_unlock();
164         return ret;
165 }
166
167 static int get_task_ioprio(struct task_struct *p)
168 {
169         int ret;
170
171         ret = security_task_getioprio(p);
172         if (ret)
173                 goto out;
174         ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM);
175         task_lock(p);
176         if (p->io_context)
177                 ret = p->io_context->ioprio;
178         task_unlock(p);
179 out:
180         return ret;
181 }
182
183 int ioprio_best(unsigned short aprio, unsigned short bprio)
184 {
185         if (!ioprio_valid(aprio))
186                 aprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM);
187         if (!ioprio_valid(bprio))
188                 bprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM);
189
190         return min(aprio, bprio);
191 }
192
193 SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
194 {
195         struct task_struct *g, *p;
196         struct user_struct *user;
197         struct pid *pgrp;
198         kuid_t uid;
199         int ret = -ESRCH;
200         int tmpio;
201
202         rcu_read_lock();
203         switch (which) {
204                 case IOPRIO_WHO_PROCESS:
205                         if (!who)
206                                 p = current;
207                         else
208                                 p = find_task_by_vpid(who);
209                         if (p)
210                                 ret = get_task_ioprio(p);
211                         break;
212                 case IOPRIO_WHO_PGRP:
213                         if (!who)
214                                 pgrp = task_pgrp(current);
215                         else
216                                 pgrp = find_vpid(who);
217                         read_lock(&tasklist_lock);
218                         do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
219                                 tmpio = get_task_ioprio(p);
220                                 if (tmpio < 0)
221                                         continue;
222                                 if (ret == -ESRCH)
223                                         ret = tmpio;
224                                 else
225                                         ret = ioprio_best(ret, tmpio);
226                         } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
227                         read_unlock(&tasklist_lock);
228
229                         break;
230                 case IOPRIO_WHO_USER:
231                         uid = make_kuid(current_user_ns(), who);
232                         if (!who)
233                                 user = current_user();
234                         else
235                                 user = find_user(uid);
236
237                         if (!user)
238                                 break;
239
240                         for_each_process_thread(g, p) {
241                                 if (!uid_eq(task_uid(p), user->uid) ||
242                                     !task_pid_vnr(p))
243                                         continue;
244                                 tmpio = get_task_ioprio(p);
245                                 if (tmpio < 0)
246                                         continue;
247                                 if (ret == -ESRCH)
248                                         ret = tmpio;
249                                 else
250                                         ret = ioprio_best(ret, tmpio);
251                         }
252
253                         if (who)
254                                 free_uid(user);
255                         break;
256                 default:
257                         ret = -EINVAL;
258         }
259
260         rcu_read_unlock();
261         return ret;
262 }